School of Agriculture and Biotechnology
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Item Effect of Intercropping on Potato Bacterial Wilt Disease and Tuber Yield in Kenya(Karatina University, 2023-12-06) MUSAH, S.M.; Birithia, R.K.; Kamiri, H.W.; Kahariri, E.Potato (Solanum tuberosum L.) is a major tuber crop in Kenya, whose productivity is heavily impaired by bacterial wilt disease, caused by Ralstonia solanacearum (Smith). Existing management strategies have not been effective, owing to the diversity and robustness of the pathogen and variation in the host range. The objective of this study was to evaluate the effectiveness of intercropping on the incidence of bacterial wilt and yield of potato in Kenya. A field experiment was conducted in four potato-growing counties, namely; Nyandarua, Nakuru, Bomet and Bungoma in Kenya. Treatments included intercroping with spring onion (Allium fistulosum L.); garden pea (Pisum sativum L.); and cabbage (Brassica oleracea var. capitata L.). Treatments also included a pure stand of potato as the control. Generally, intercropping had a significant suppressive effect (P<0.05) on the incidence and severity of bacterial wilt disease. Intercropping potato with spring onion, in particular, had the highest disease suppressive effect, followed by intercropping potato with cabbage; and lastly by potato with garden pea. Accordingly, potato-onion intercrop recorded the highest potato tuber yield (12.9 t ha-1), while the potato pure stand recorded the lowest tuber yield (7.9 t ha-1). Bacterial wilt disease incidence positively correlated with disease severity (r = 0.931; P<0.05). In contrast, the disease incidence and severity negatively correlated with tuber yield. In terms of Land Equivalent Ratio (LER), the highest value (1.64) was with potato-onion intercrop; and the lowest (1.35) with the potato-garden pea intercrop.Item Farmers' Preference for Onion Varieties and Implications of Knowledge of Iris Yellow Spot Disease in Kenya(African Crop Science Journal, 2021-03) Subramanian, S.; Birithia, R.K.; Kuria, D.K.Thrip transmitted Iris yellow spot disease (IYSD) is an economically important viral disease, affecting bulb onions worldwide. Recommended IYSD resistant varieties are not commonly grown in countries like Kenya, yet inappropriate disease control measures are applied upon disease occurrence in the fields. This is presumably due to lack of knowledge on the disease and/or recommended varieties do not match farmers’ preferred traits. The objective of this study was to assess farmers’ knowledge of IYSD and their criteria for selecting onion varieties for/against IYSD in Kenya. A study was conducted with 360 respondents across three onion growing agro-ecological zones (AEZ) in Kenya, during 2019- 2020. Farmers’ fields were assessed for IYSD incidence and severity. All farmers acknowledged the existence of IYSD based on diseased plants in the field. However, majority of the farmers (95.6%) were not aware of the cause of the disease. Onion thrips and IYSD susceptible red onion varieties were the most preferred (77.9%) by farmers. Preference for these varieties was based on their high yielding capacity, early maturity, strong pungency, marketability and long shelf life. Most farmers (59.8%) relied on fungicides to control IYSD, though ineffectively. Lack of appropriate management strategies for IYSD was due to lack of knowledge on the disease diagnosis, epidemiology as well as cultivation of IYSD susceptible red varieties.